Fourth species counterpoint is the species of the suspension: a consonant note is held over a beat where it becomes dissonant, then resolves downward by step. Suspensions are among the most expressive sounds in all of Western music.
The Suspension: Delayed Resolution
A suspension is a three-part rhythmic-harmonic event: preparation (a consonant note sounding on a weak beat or at the end of one unit), suspension (that same note held over into a strong beat where the other voice has moved, creating a dissonance), and resolution (the suspended note steps downward by one step to a consonance). The standard analytic notation labels the suspension by the interval at the moment of dissonance followed by the interval at the moment of resolution: 4-3 (a fourth suspended resolving to a third), 7-6 (a seventh resolving to a sixth), 9-8 (a ninth resolving to an octave), 2-3 (a second in the bass resolving to a third — the bass suspension).
The emotional power of suspensions is profound. The moment of suspension — when the held note clashes against the new harmony — creates pain, yearning, or tension. The resolution — when the held note finally steps down to consonance — creates relief, satisfaction, or rest. This tension-release pair is one of the most fundamental emotional mechanisms in Western music. Fux, writing in 1725, calls the suspension the "ornament" of counterpoint. Rameau, writing at the same time, recognises that suspensions create the most powerful cadences. Every composer from Palestrina to Beethoven to Antônio Carlos Jobim uses them constantly, and the Bach chorale repertoire contains literally hundreds of textbook suspensions.
Fourth Species Rules
In fourth species, the counterpoint voice moves in half notes, but each note is tied over from the previous beat — so the first note of each measure is held from the second half of the previous measure, creating a continuous syncopation. Only the half note on the second beat of each measure is "fresh" (struck new). The first beat of each measure (the downbeat) is always the held-over note, which may be dissonant if it is a valid suspension.
The valid suspension types in two-voice counterpoint are limited:
- 7-6 suspension — the most common and smooth. The seventh above the cantus firmus resolves down to the sixth. The interval pair sounds plaintive and conversational.
- 9-8 suspension — a powerful octave resolution that creates a strong sense of arrival. Less common than 7-6 because the resolution to the octave may sound too final mid-phrase.
- 4-3 suspension — very common and expressive. The fourth above the bass resolves down to the third. This is the basis of the cadential 6/4 in tonal harmony.
- 2-3 bass suspension — the only valid suspension below the cantus firmus. The bass note creates a second against the upper voice, then descends a step to a third below. The resolution is still downward by step, but because the dissonant note is in the bass, the interval ratio appears inverted.
The 7-6 and 4-3 are by far the most frequently used in the actual repertoire. Resolution must be by step downward (in the suspending voice). Upward resolution is called a retardation and is only permitted in specific circumstances: the 7-8 resolution in the soprano is sometimes permitted in late-Baroque practice; the 4-5 is generally prohibited because it produces a perfect fifth on a weak beat that fails to resolve the suspension's tension.
The Chain of Suspensions
One of the most beautiful effects in fourth species — and in tonal music generally — is the chain of suspensions: a series of suspensions in which the resolution of one suspension immediately becomes the preparation of the next. A 7-6 chain might run: 7-6, 7-6, 7-6 over several measures, with the bass moving down by step and the upper voice moving in delayed parallel sixths. Such chains create a sense of irresistible descent, of grief or gravity. Chains of 7-6 suspensions are a hallmark of Palestrina's style and of later Baroque slow movements.
The 4-3 chain over a descending bass is equally common and forms the foundation of countless lamenting passages, including Purcell's Dido's Lament and Bach's Crucifixus from the B minor Mass. The descending tetrachord (a stepwise descent from tonic to dominant in the bass) almost always invites suspensions in the upper voices.
Suspensions in Tonal Music
Once you understand suspensions in species counterpoint, you will hear them constantly in tonal music. The seventh of V7 (for example F over G in C major) behaves like a suspended dissonance: it must resolve down by step, to E, when the chord resolves to I. The augmented sixth chord functions partly as a double suspension that resolves to the dominant. Every cadential 6/4 chord (the second-inversion tonic chord that typically precedes the dominant at a cadence) contains a double suspension: the 6 resolves to 5 and the 4 resolves to 3, producing the V chord.
Jazz harmony makes extensive use of suspensions: the "sus" chord (Csus4 = C, F, G) is literally a suspension of the third by the fourth, and may resolve down to C major or may stand on its own as a stable modal sonority. The same applies to the various extended dominants (9, 11, 13) which behave as stacked suspensions over the basic triad.
Breaking the Suspension
Fourth species permits the counterpoint to "break" the syncopation pattern when no good suspension is available — that is, to abandon the tied note and instead write a fresh half note on the downbeat. Frequent breaks indicate that the counterpoint is failing to find the suspension chain that the cantus firmus invites; ideally, the exercise should be largely or entirely syncopated, with breaks only at the cadence and at one or two points where the available intervals simply will not produce a valid suspension.
Practical Exercise
On the same cantus firmus used in previous species, write a fourth species counterpoint. Begin with a consonance at the start. On the second half note, tie it over into the next measure's downbeat. Is the held note dissonant against the new cantus firmus note? If so, identify the suspension type (7-6, 4-3, 9-8) and resolve it downward by step on the second half note. If the held note is consonant (not a valid suspension interval), simply hold it as a consonance and try to arrange the second half note of the measure as a preparation for the next suspension. Aim for a chain of three or more suspensions in succession somewhere in the exercise.
Sources and Further Reading
- Fux/Mann. The Study of Counterpoint. Norton. Part II, Chapter 5.
- Jeppesen. Counterpoint. Prentice-Hall. Chapter 7.
- Aldwell and Schachter. Harmony and Voice Leading. Schirmer/Cengage. Chapter 10: Suspensions.
- Open Music Theory — Suspensions (openmusictheory.net, CC BY-SA 4.0).
- Gauldin. A Practical Approach to 18th-Century Counterpoint. Waveland Press. Chapter 5.